/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/intrin/strace.h"
#include "libc/nt/enum/processcreationflags.h"
#include "libc/sysv/pib.h"

/**
 * Creates session and sets the process group id.
 *
 * On Windows, this operation won't take effect until fork() or execve()
 * is called, which use CreateProcess(CREATE_NO_WINDOW|DETACHED_PROCESS)
 * to ensure the process won't be killed when the terminal closes. It is
 * meant primarily to be used by daemon() which is the api that you want
 *
 * @return new session id, or -1 w/ errno
 * @raise EPERM if already the leader
 */
int setsid(void) {
  int rc;
  if (!IsWindows() && !IsMetal()) {
    rc = sys_setsid();
  } else {
    // this ensures that second fork() call in daemon() will create a
    // process that will not be killed when the console window closes
    __get_pib()->dwCreationFlags |= kNtCreateNoWindow | kNtDetachedProcess;
    rc = getpid();
  }
  STRACE("setsid() → %d% m", rc);
  return rc;
}
